docs: def make_processor(func, arg=None):
      """
      A pre-called processor that wraps the execution of the target callable ``func``.
  
      This is useful for when ``func`` is a third party mapping function that can take your column's
      value and return an expected result, but doesn't understand all of the extra kwargs that get
      sent to processor callbacks.  Because this helper proxies access to ``func``, it can hold back
      the extra kwargs for a successful call.
  
      ``func`` will be called once per object record, a single positional argument being the column
      data retrieved via the column's :py:attr:`~datatableview.columns.Column.sources`
  
      An optional ``arg`` may be given, which will be forwarded as a second positional argument to
      ``func``.  This was originally intended to simplify using Django template filter functions as
      ``func``.  If you need to sent more arguments, consider wrapping your ``func`` in a
      ``functools.partial``, and use that as ``func`` instead.
      """
      def helper(instance, *args, **kwargs):
          value = kwargs.get('default_value')
          if value is None:
              value = instance
          if arg is not None:
              extra_arg = [arg]
          else:
              extra_arg = []
          return func(value, *extra_arg)
      return helper